Japan Launches Historic Mission to Grab Samples From a Moon of Mars
Finn's Take· TL;DR- Japan launched its first mission to land on Phobos, a Mars moon, and return samples to Earth in 2031.
- Scientists hope samples reveal how Phobos formed and whether Mars once supported life with water and atmosphere.
- An international partnership led by JAXA will deploy a rover to study the moon's surface despite its extremely low gravity.
A First-of-Its-Kind Journey to the Mars System
Japan's Martian Moons eXploration mission, known as MMX, will be the first mission to land on Phobos and the first to return a sample from the Mars system to Earth. Today, Monday, October 19, the MMX mission lifted off at 3:41 p.m. EDT aboard an H3 rocket from Tanegashima Space Center in southern Japan. It is a landmark moment not just for Japan, but for planetary science as a whole — a five-year voyage to one of the most mysterious and overlooked corners of our solar system.
JAXA calls MMX "the largest international collaborative mission in lunar and planetary exploration ever led by Japan." MMX is led by the Japanese Aerospace Exploration Agency (JAXA), in collaboration with the US, France, Germany, and the European Space Agency. The sheer breadth of that partnership reflects just how scientifically significant this mission is considered to be.
What Scientists Hope to Uncover
MMX has two main science goals: figure out how Phobos and Deimos formed, and investigate the origins of a Mars long since gone, which once had a thick atmosphere and liquid water on its surface — and the team believes the answers might be connected. Scientists are still debating the moons' origin: are they the result of a giant impact between Mars and another celestial body in the primeval solar system, or are they asteroids captured into the red planet's orbit? Settling that debate could reshape our understanding of how the entire inner solar system evolved.
By returning material from Phobos and conducting observations of the moons, the origin of the Mars system and the pathways for the emergence of habitability and life can be explored. The mission is designed to return at least 10 grams of material from the moon's surface — a tiny amount, but one that scientists say could be extraordinarily revealing. NASA will receive and curate about 15% of the returned sample at the Johnson Space Center's astromaterials lab in Houston.
A Spacecraft, a Rover, and a Very Long Road
The main MMX spacecraft will study Phobos from a distance, then deploy a rover called IDEFIX to the moon's surface, before finally landing on Phobos to collect samples to return to Earth. IDEFIX, a 55-pound rover built by Germany's space agency DLR and France's CNES, will be dropped onto Phobos and spend about three months studying its surface. The gravity on Phobos is so low that IDEFIX will only weigh the equivalent of 15 grams on its surface. That near-weightless environment poses unique engineering challenges that have never been tackled before.
MMX will use two different instruments to try collecting samples from Phobos: a robotic-arm-mounted corer, and a system that works by releasing pressurized gas to kick up surface materials that then travel through a tube into a collection container. After launch, the spacecraft is expected to reach Mars in August 2027 and begin surveying both moons, with Phobos sample collection planned for no earlier than December 2028 and the return to Earth in 2031.
A History of Failed Attempts — and Why This Time Is Different
Reaching Phobos has proven notoriously difficult. There have been multiple Soviet and Russian attempts to reach the moon from the late 1980s through 2011, all of which ended in failure. The Martian moons remain particularly mysterious, with major open questions about how they formed and what they are made of — and so far, no spacecraft have dwelled near the Martian moons for very long, leaving scientists with little more than what a few fly-by measurements have revealed.
The MMX mission aims to uncover the origin of the Martian moons and investigate how the planetary formation process unfolded in the transition region between the inner and outer solar system, including mechanisms that transported key materials — such as water and organic matter — necessary for the emergence and habitability of life on terrestrial planets. If all goes according to plan, the samples will arrive on Earth in 2031, giving scientists their first direct look at material from the Martian sphere — and potentially answering questions about our solar system that have lingered for decades.